Development of Hard Winter Wheat after Anthesis as Affected by Nitrogen Nutrition1

Post‐anthesis nitrogen nutrition should be an important determinant of wheat (Triticum aestivum L.) grain yield because remobilization of vegetative N for grain filling is associated with decreasing photosynthetic activity of leaves. Experimental evidence is contradictory, however. Research was conducted to reconcile different findings on the importance of N nutrition of wheat during grain development and to understand the inverse grain yield/N concentration relationship. Five winter wheat genotypes were grown in sand with nutrient solution in a glasshouse. Two N regimes were imposed at the early boot stage (Feekes scale 9) by continuing the complete nutrient solution by leaching nutrients and supplying solution devoid of N until plants were mature. Plants were harvested 10, 20, or 40 days after anthesis and analyzed for grain and vegetative yields, yield components, and grain and vegetative N concentrations. High N nutrition increased mean biological dry matter yield and grain yield 20 and 40 days after anthesis. Grain yield was significantly correlated with number of spikes per plant, kernels per plant, kernels per spike, and kernel weight. Fertile spikes per plant were affected most by N nutrition, but grain growth rates per plant and per kernel also occasionally increased. Grain N concentration remained nearly constant under low N nutrition, but increased between the first and last samplings under high N nutrition. Vegetative N content wits also nearly constant under high N nutrition, but decreased under low N nutrition as grain filling progressed. We concluded Ihat ample levels of N during late developmental stages are necessary for maximum yields of high‐protein grain.